1. Field of the Invention
The present invention generally relates to a recording/reproducing apparatus for conducting a recording and/or reproducing process with respect to a recordable disk having flexibility, and a disk cartridge for accommodating a recordable disk.
2. Description of the Related Art
Recently, since a digitized television broadcast service has begun, it has been required for an information recording medium to record a large amount of digital data. For example, in the optical disk field, minimizing a light spot diameter condensed on an optical disk to record or reproduce digital data is one of basic methods of high density development. Hereinafter, an optical disk will be mainly described but the present invention is not limited to the optical disk, and the recordable disk according to the present invention used for a recording/reproducing apparatus can be any type of recording disk having a disk shape such as a phase change memory, a magnetic optical memory, or a hologram memory.
Accordingly, in optical disk development, it is required to shorten a light wavelength used for recording/reproducing digital data and to increase an aperture number NA of an objective lens. For the light wavelength, a wavelength being 789 nm of a near-infrared light is used for a CD (Compact Disk), and a wavelength being in the vicinity of 650 nm of a red light is used. Recently, a semiconductor laser having a blue-violet light has been developed. After this, a laser beam being in the vicinity of 400 nm will be used.
In the objective lens, the aperture number NA for the CD is less than 0.5 but the aperture number NA for the DVD (Digital Versatile Disk) is approximately 0.6. In the future, it is required for the aperture number NA to be greater than 0.7. However, when the aperture number NA of the objective lens becomes greater and the light wavelength becomes shorter, an aberration occurs more often at an aperture diaphragm. Thus, the margin for a tilt of the optical disk is reduced. In addition, the focus depth becomes smaller since the aperture number NA becomes greater. Accordingly, it is required to improve the accuracy of a focus servo.
Moreover, when the objective lens having a larger aperture number NA is used, a distance between the objective lens and a recording surface of the optical disk becomes shorter. Thus, surface vibration of the optical disk should be suppressed smaller or a pickup problem can be caused by a crash between the objective lens and the optical disk that may occur just before the focus servo is activated.
As a high-capacity optical disk having a short wavelength and a high aperture number NA, for example, a system is proposed in IDS 1, in that a recording film is formed on a substrate being the same thickness as a CD and having greater rigidity, and data are recorded and reproduced with respect to the recording film where a light for recording and reproducing data passes inside through a thin cover layer but does not pass through the substrate.
For example, IDS or Cross-References 1 through 5 disclose a recording/reproducing apparatus configured in that an optical disk having flexibility is based on a stabilizing member and rotated so as to suppress surface vibration and stabilize the optical disk by utilizing aerodynamic action force based on Bernoulli's principle.
[IDS or Cross-Reference 1]
Japanese Laid-Open Patent Application No. 7-105657
[IDS or Cross-Reference 2]
Japanese Laid-Open Patent Application No. 10-308059
[IDS or Cross-Reference 3]
United State Patent Application Publication No. 2002/0186636
[IDS or Cross-Reference 4]
Japanese Laid-Open Patent Application No. 2002-269855
[IDS or Cross-Reference 5]
Japanese Laid-Open Patent Application No. 2002-358759
[IDS 1]
O Plus E, vol. 20, no. 2, p. 183.
[IDS 2]
“Optical Readout of Videodisc”, IEEE Transaction on Consumer Electronics, November, 1976, pp. 304–308
However, in conventional technologies above-described, in order for the surface vibration and the tilt of the optical disk being rotated to be smaller in a case in that the substrate of the optical disk is formed by a rigid body, it is required to make a perfect form and to form the recording film at lower temperature to prevent deformation caused by heat. As a result, tact time of an optical disk production becomes longer and production cost increases.
Moreover, in a configuration of rotating the optical disk having flexibility on a stabilizing board as disclosed in the IDS or Cross-References 1 through 3, the risk of the optical disk making contact with and sliding on the stabilizing board is increased and a disk surface or a stabilizing board surface are damaged. In addition, an error can occur due to dusts caused by this sliding.
In particular, as disclosed in the IDS or Cross-Reference 1, in a configuration in that the recording film is formed at a stabilizing board side, the recording film of the optical disk is damaged by the sliding and then this damage causes an error directly. Moreover, in a case in that a flat stabilizing board is simply used, a reduction effect on the surface vibration of the optical disk is limited. Thus, in a case of using the objective lens having the greater aperture number NA, the risk of a crash of the objective lens and the optical disk still remains.
One of methods using the stabilizing board is disclosed in the IDS 2. In a configuration disclosed in the IDS 2, a flexible disk is clamped and rotated in a narrow gap formed by members configured by two stabilizing members functioning as U-shaped stabilizers, so as to dramatically suppress the surface vibration of the optical disk to be less. As disclosed in IDS 2, a space between the flexible disk and each of the stabilizing members in the gap is 25 μm, which is narrow. Dust is drawn into the space between the flexible disk and each of the stabilizing members and the recording film is damaged. Then, there is a risk in that this damage directly causes an error. In particular, in this configuration, since the stabilizing members always contact with both front and rear surfaces of the flexible disk, even if an information recording part is provided to both the front and rear surfaces, the risk can not be eliminated.
According to the invention disclosed in IDS or Cross-Reference 3, the surface vibration of a flexible optical disk can be certainly suppressed, data can be recorded at higher density, and the objective lens can be prevented from sliding and contacting the flexible optical disk. However, in practice, complicated location adjustment control is required with respect to the stabilizing guide members and a recording/reproducing head. Accordingly, not only does the workload of a drive control system become greater, but also the apparatus cost increase.